The present invention relates to locks, and in particular, to an adjustable friction lock arrangement for rods, tubes, and the like.
A variety of locking devices are available for interconnecting different elements of a telescoping assembly. One type of locking device comprises a clamp, which is selectively manipulated to abuttingly engage an adjacent portion of the assembly and frictionally retain the same in place. Such adjustable locks are typically easy to use, but generally do not provide very substantial supporting strength. Hence, it would be quite advantageous to provide a friction-type of lock which is capable of supporting extremely large weights, while having an engaging arrangement which when locked, will not permanently deform the element clamped, so that it may be used repeatedly in a variety of different positions without weakening or damaging any of the members of the assembly.
One example of a clamp-type adjustable lock is disclosed in U.S. Pat. No. 2,893,766 to Meyer, which includes a rod-like member retained parallel with another rod-like member having an eccentric cross-sectional shape. A helical coil surrounds the two rod members, so that when the eccentric rod is rotated, the helical spring is tensed, thereby frictionally engaging two rods, and interconnecting the same. One problem associated with this type of lock is that the weight supporting capacity of the lock is limited, since the clamping forces are generated solely by the resiliency of the helical spring. Further, this type of prior art device is somewhat difficult to assemble, and therefore has restricted practical applications.
A non-frictional locking device is disclosed in U.S. Pat. No. 4,111,470 to Welcker, which includes an eccentric key that is carried in a hollow tubular member. The tubular element receives a second hollow rod element therein, with a notch in which the key is pivoted to positively interconnect the two tubular sections. Although this type of couple securely interconnects the two members of the assembly, it does not employ a frictional type of lock, such that there are only a predetermined number of positions in which the tubular segments can be interconnected.